Problem: At the party, Aisha and her friends ate $2 \dfrac{1}{2}$ pizzas. After the party, there were $1 \dfrac{1}{8}$ pizzas left. How many pizzas were there at the start of the party?
To find the total number of pizzas at the start of the party, we need to add. $2\frac{1}{2}$ $1\frac{1}{8}$ amount of pizzas to start pizzas eaten pizzas left ${2 \dfrac{1}{2}} + 1 \dfrac{1}{8}} = {\text{ amount of pizza to start}}$ Our denominators need to be the same so we can add. What is the least common multiple for the denominators $2$ and $8}$ ? The least common multiple of $2$ and $8}$ is ${8}$. $\dfrac{{1}\times 4}{{2}\times 4} = {\dfrac{4}{8}}$ Now we can add our fractions. $\begin{aligned} &{2} &{\dfrac4{8}}\\\\ +&1}&\dfrac{1}{8}}\\ \hline\\ &&{\dfrac{5}{8}}\\ \end{aligned}$ Lastly, we can add our whole numbers. $\begin{aligned} &{2} &{\dfrac4{8}}\\\\ +&1}&\dfrac{1}{8}}\\ \hline\\ &3&{\dfrac{5}{8}}\\ \end{aligned}$ There were ${3\dfrac{5}{8}}$ pizzas at the start of the party. This can also be written as ${\dfrac{29}{8}}$ pizzas.